The present invention relates to a device to measure the flow of a fluid flowing through a measuring pipe, the device includes a coil arranged above the measuring pipe, a coil arranged below the measuring pipe, and a pair of electrodes facing one another, on the side of the measuring pipe, wherein the coils are excitable and produce both aiding and opposing magnetic fields. A correction circuit is provided for correcting the voltage between the electrodes which is only approximately proportionate to the flow of the fluid in the presence of aiding magnetic fields The correction circuit provides a correction function to an output signal proportionate to the flow of the fluid depending on the voltages between the electrodes in the presence of aiding and opposing magnetic fields.
A device of this type is known. It also permits measuring when the measuring pipe is not completely filled.
The fluid flow through the measuring pipe can correspond to a "flowing movement" or to a "rushing movement" (viz. the book by Bohl "Technische Stromungslehre", 9th edition, Section 4.4.3). A flowing movement is characterized by a Froude number Fr which is less than 1, a rushing movement by a Froude number Fr which is greater than 1.
The known device cannot distinguish between a flowing movement and a rushing movement.
The invention starts out from the knowledge that a relation between the voltage corresponding to the aiding magnetic fields and the correction function allows such a distinction. If this relation is utilized, one of two different correction functions can be employed depending on whether the flow is flowing or rushing in order to obtain an output signal which is independent of the state of movement.